The most useful glass block to use on the exterior walls of the house is the light colored glass block which does not fade in sunlight and these glass blocks are the most popular at present.

brown wave glass block

Dark colored glass blocks are made by injecting dyes of various beautiful colors into the inside of the glass block.
 Therefore, the ultraviolet rays in the sunlight deactivate the colors of the ink coated on the glass block.

Red wave glass block